Printing ink

Abstract

To provide a water-based printing ink that suppresses plate blinding during printing, exhibits superior humid blocking resistance, scratch resistance, and tape adhesion in the printed layer, and maintains superior temporal stability in a two-pack formulation after addition of a curing agent to the printing ink.SOLUTION: The present invention provides a printing ink comprising a colorant, a water-based urethane resin, a wax, and an aqueous solvent, wherein the wax contains a structural unit represented by the following general formula (1), in an amount of 50 mass% or more based on the total wax; the wax has a weight-average molecular weight of 1,000 to 2,400,000; and the content of the wax is 0.1 to 6 mass% based on the total printing ink. (R1 represents a hydrocarbon group having 1-24 carbon atoms.)SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a printing ink containing a colorant, an aqueous urethane resin, a wax, and an aqueous solvent.

Background Art

[0002] Gravure or flexographic inks are widely used as pattern inks for the purpose of imparting cosmetic and functional properties to printed objects. In recent years, however, the requirements for printing inks have diversified year by year, such as the diversity of packaging materials, the sophistication of packaging technologies, and efforts to address environmental issues related to regulations represented by organic solvents.

[0003] In recent years, conversion to aqueous printing inks has been proposed as a means to solve environmental protection and regulatory issues. Aqueous printing inks have been widely used for printing on paper products such as general wrapping paper and cardboard. However, in the field of printing on non-permeable plastic film substrates mainly for packaging materials, there are still many problems compared with solvent-based printing inks.

[0004] Also, based on the concept of carbon neutrality that using biomass raw materials such as plant raw materials and making the amount of carbon dioxide emitted by combustion the same as the amount of carbon dioxide absorbed and fixed by the growth of plants etc. will not increase carbon dioxide in the air, using raw materials derived from biomass for resins etc. used in printing inks is considered effective in avoiding an increase in carbon dioxide, which is a greenhouse gas (Patent Document 1).

[0005] The quality of printing ink mainly depends greatly on its binder resin, which is the main component. Even in the case of aqueous printing inks, aqueous urethane resins are widely used as the main binder resin in consideration of generalization and high performance. This is because aqueous urethane resins enable free coating film design from hard and tough coating films to soft and elastic coating films. Among them, aqueous printing inks using aqueous urethane resins containing polyether polyols are known to have high flexibility and good adhesion to plastic substrates. For example, Patent Documents 2 and 3 disclose the technical development of aqueous printing inks using aqueous urethane resins composed of polytetramethylene glycol and polyethylene glycol. However, in the case of aqueous printing inks, the technical difficulty regarding the ink film physical properties such as plate clogging property during printing, laminating strength against various plastic film substrates, and blocking resistance is high, and it is still in the development stage.

[0006] Furthermore, Patent Document 4 discloses an aqueous ink using an aqueous urethane resin containing biomass polyol. However, in the case of aqueous ink, it is very difficult to control the plate clogging property, and the addition of wax, which is essential for preventing blocking and damage of printed matter, is one of the major factors that deteriorate the plate clogging property. Therefore, it has been difficult to solve the problem with an improvement approach based only on the resin.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to provide an aqueous printing ink in which plate clogging property during printing is suppressed, and the printing layer has good humidity-resistant blocking property, scratch resistance, tape adhesiveness, and two-component stability over time after adding a curing agent to the printing ink.

Means for Solving the Problems

[0009] In view of the above situation, the present inventor has conducted intensive studies and as a result, found that the problems can be solved by using the water-based printing ink described below, and thus completed the present invention.

[0010] That is, the present invention relates to a printing ink containing a colorant, an aqueous urethane resin, a wax, and an aqueous solvent, wherein the wax contains 50% by mass or more of a structural unit represented by the following general formula (1) based on the whole wax, the weight average molecular weight of the wax is from 1,000 to 2,400,000, and the printing ink contains 0.1 to 6% by mass of the wax based on the whole printing ink.

[0011] General formula (1)

Chemical formula

[0012] Further, the present invention relates to any of the above printing inks, wherein the structural unit represented by the general formula (1) is derived from biomass.

[0013] Further, the present invention relates to any of the above printing inks, wherein the aqueous urethane resin is made from a polyol derived from biomass.

[0014] Further, the present invention relates to any of the above printing inks, wherein the particle size of the wax is from 0.1 to 10 μm.

[0015] Further, the present invention relates to any of the above printing inks, wherein the biomass degree of the printing ink is 10% by mass or more.

[0016] Further, the present invention relates to any of the above printing inks, which is a printing ink for back printing.

Advantages of the Invention

[0017] According to the present invention, it has become possible to provide an aqueous printing ink that suppresses plate clogging during printing, has good leveling properties, and has good humidity-resistant blocking properties, scratch resistance, tape adhesiveness, and two-component stability over time after adding a curing agent to the printing ink.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the constituent elements and embodiments of the present invention will be described in detail. However, these embodiments are merely examples in the invention and are not limited to these descriptions as long as the gist is not impaired. Also, unless otherwise specified, “%” and “parts” represent “mass %” and “parts by mass”, respectively. Also, the printing ink may be abbreviated as ink.

[0019] <Printing Ink> The present invention relates to a printing ink containing a colorant, an aqueous urethane resin, a wax, and an aqueous solvent, and is preferably used in the form of reverse printing lamination.

[0020] <Wax> By containing a wax having a structural unit represented by the general formula (1), the printing ink maintains good humidity-resistant blocking properties and scratch resistance, and suppresses a decrease in plate clogging, which can be regarded as an adverse effect of adding wax in the printing ink. Even when contained in an amount much larger than the usual wax usage amount, it is possible to maintain good plate clogging properties.

[0021] Furthermore, the wax having a structural unit represented by the general formula (1) can use biomass-derived raw materials, which also contributes to environmental protection. Biomass-derived means natural products such as plants, metabolites of microorganisms, extracts of natural products and metabolites, or synthetic compounds using these as raw materials. That is, the biomass raw material means that at least a part of the contained carbon atoms includes carbon atoms contained in natural products or metabolites. In addition, the biomass content referred to in the present invention indicates the mass percentage of biomass-derived components when the solid content of the object is 100% by mass. However, when the object is the above-mentioned composite and a raw material not derived from biomass is used during synthesis, it is the value obtained by subtracting the equivalent amount of the raw material not derived from biomass.

[0022] General formula (1)

Chemical formula

[0023] General formula (1) is a residue of a hydroxy aliphatic carboxylic acid or its polymer, and the carbon number of R 1 is 1 to 24, preferably 2 to 6. R 1 If it is within this range, as the action of the wax, the printing layer has practical moisture resistance to blocking and scratch resistance performance.

[0024] The polymer of hydroxy aliphatic carboxylic acid can be obtained according to a known method, for example, according to Japanese Patent Application Laid-Open No. 2012-139835. Polylactic acid (carbon number of R 1 is 2) and polyhydroxybutyric acid (carbon number of R 1 is 3) are also available as biomass raw materials. In addition, the wax in the present invention contains 50% by mass or more, preferably 80% by mass or more, more preferably 98% by mass or more of the structural unit represented by the general formula (1) with respect to the whole wax. Its form may be a mixture of polyhydroxy aliphatic carboxylic acid and others, or a copolymer of polyhydroxy aliphatic carboxylic acid and a hydroxycarboxylic acid other than polyhydroxy aliphatic carboxylic acid.

[0025] The weight average molecular weight Mw of the above wax is 1000 to 2400000, preferably 20000 to 600000. If it is within the above range, the wax can be stably dispersed in the ink. When the upper limit is exceeded, the dispersibility in the ink becomes unstable, and separation, sedimentation, thickening, etc. of the ink over time may hinder the original printing.

[0026] The particle size of the wax is preferably 0.1 to 10 μm. Preferably, it is 1 to 7 μm, more preferably 3 to 6 μm. The particle size of the wax refers to that measured by the laser diffraction scattering method.

[0027] The biomass degree of the above wax is preferably 98% by mass or more. Further, the biomass degree in the non-volatile content of the ink containing the above wax in the present invention, that is, the biomass degree of the printed layer is preferably 5% by mass or more, preferably 7% by mass or more, and still more preferably 10% by mass or more.

[0028] <Colorant> The printing ink of the present invention contains a colorant. It is preferable to use an inorganic pigment or an organic pigment for the colorant. The C.I. pigments described in the Color Index can be appropriately used. Examples of the inorganic pigment include titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, aluminum hydroxide, chromium oxide, silica, carbon black, aluminum, mica, etc. From the viewpoints of coloring power, hiding power, chemical resistance, and weather resistance, titanium oxide is preferable as the white pigment, and further, titanium oxide with a basic pigment surface is more preferable. Aluminum is in powder or paste form, but it is preferably used in paste form from the viewpoints of handleability and safety, and either leafing or non-leafing may be used. Barium sulfate, calcium carbonate, and aluminum hydroxide are called extender pigments and are used as extenders to improve fluidity, strength, and optical properties. Examples of the above organic pigment include, but are not limited to, the following: soluble azo-based, insoluble azo-based, azo-based, phthalocyanine-based, halogenated phthalocyanine-based, anthraquinone-based, ansanthrone-based, dianthraquinone-based, anthrapyrimidine-based, perylene-based, perinone-based, quinacridone-based, thioindigo-based, dioxazine-based, isoindolinone-based, quinophthalone-based, azomethine azo-based, flavanthrone-based, diketopyrrolopyrrole-based, isoindoline-based, indanthrone-based, carbon black-based pigments, etc. Also, for example, Carmine 6B, Lake Red C, Permanent Red 2B, Disazo Yellow, Pyrazolone Orange, Carmine FB, Chromophthal Yellow, Chromophthal Red, Phthalocyanine Blue, Phthalocyanine Green, Dioxazine Violet, Quinacridone Magenta, Quinacridone Red, Indanthrone Blue, Pyrimidine Yellow, Thioindigo Bordeaux, Thioindigo Magenta, Perylene Red, Perinone Orange, Isoindolinone Yellow, Aniline Black, Diketopyrrolopyrrole Red, daylight fluorescent pigments, etc. can be mentioned, and those described in the Color Index can be used in combination at any time.

[0029] <Waterborne urethane resin> The printing ink of the present invention contains a waterborne urethane resin. The waterborne urethane resin functions as a pigment dispersion resin and a binder resin. The mass average molecular weight of the waterborne urethane resin is preferably 10,000 to 100,000. More preferably, it is 20,000 to 80,000. When the mass average molecular weight is within the range of 10,000 to 100,000, the laminating strength tends to improve.

[0030] From the concept of carbon neutrality, the biomass degree of the waterborne urethane resin in the present invention is preferably 30% by mass or more, and still more preferably 40% by mass or more, in the total mass of the waterborne urethane resin.

[0031] The waterborne urethane resin in the present invention preferably has an acidic group such as a carboxyl group for water solubilization. For example, a polyurethane resin obtained by subjecting a polyol, a polyhydroxycarboxylic acid, and a polyisocyanate to a condensation reaction can be mentioned. Also preferred is a polyurethane resin (polyurethane urea resin) obtained by reacting a urethane prepolymer having an isocyanate group at its terminal, which is obtained by a condensation reaction of a polyol, a polyhydroxycarboxylic acid, and a polyisocyanate, with a polyamine (referred to as chain extension). It is preferable that any one of the polyol, polyhydroxycarboxylic acid, polyisocyanate, and polyamine is a biomass-derived component, and it is preferable that the polyol contains a biomass-derived component (biomass-derived polyol). Usually, since the proportion of the polyol among the components of the polyurethane is higher than that of the other components, by using a biomass-derived polyol as the polyol, a higher biomass degree can be obtained than when only the other components are made of biomass-derived components, which is effective.

[0032] Such an aqueous urethane resin can be produced, for example, by the methods described in International Publication No. 2018 / 199085 and Japanese Patent Application Laid-Open No. 2018-131624.

[0033] Examples of the raw material polyol used in the production of the aqueous urethane resin include polyether polyol, polyester polyol, polycarbonate polyol, and polyolefin polyol. These are preferably used at 0 to 65% by mass in the total raw material non-volatile content.

[0034] Examples of the polyhydroxycarboxylic acid used in the production of the aqueous urethane resin include dimethylolalkanoic acids such as 2,2-dimethylolpropanoic acid, 2,2-dimethylolbutanoic acid, and 2,2-dimethylolvaleric acid, and one or more of these may be used in combination. Among them, from the viewpoint of compatibility and reactivity with other urethane raw materials, it is preferable to use 2,2-dimethylolpropanoic acid and / or 2,2-dimethylolbutanoic acid. In addition, in the production of the aqueous urethane resin, the hydroxyl group of the polyhydroxycarboxylic acid reacts with the polyisocyanate to form a urethane bond, but the carboxyl group hardly reacts with the isocyanate group, so most of it remains as a carboxyl group, is neutralized, and can be made into an aqueous urethane resin by being made aqueous.

[0035] As the polyisocyanate used in the production of the aqueous urethane resin, diisocyanate is preferred, and as such compounds, various known aromatic, aliphatic or alicyclic diisocyanates can be used. For example, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, and dimer diisocyanate obtained by converting the carboxyl group of dimer acid to an isocyanate group are representative examples. These can be used alone or in admixture of two or more. Among them, isophorone diisocyanate, tolylene diisocyanate, and 4,4'-diphenylmethane diisocyanate are preferred, and isophorone diisocyanate is more preferred from the viewpoint of solubility.

[0036] The above aqueous urethane resin is preferably chain-extended with a polyamine to have a urea bond. The aqueous urethane resin having a urea bond can be produced, for example, by previously producing a urethane prepolymer containing an isocyanate group at the terminal as a reaction product of a polyol containing at least an aliphatic polycarbonate polyol, a polyhydroxycarboxylic acid, and a polyisocyanate, and further chain-extending it with a polyamine.

[0037] When the polyamine is, for example, ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, and further dimer diamine obtained by converting the carboxyl group of dimer acid into an amino group, 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropyl ethylenediamine, di-2-hydroxypropyl ethylenediamine, etc. can be used, and preferably it is a polyamine having a hydroxyl group. By having a hydroxyl group, the solubility in water can be increased. These can be used alone or in combination of two or more. More preferably, they are isophoronediamine and 2-hydroxyethylethylenediamine (2-aminoethylethanolamine).

[0038] When performing a chain extension reaction using a polyamine, a monoamine may be used as a reaction terminator. As the reaction terminator, for example, in addition to dialkylamines such as dibutylamine, diethylamine, dipropylamine, etc., amines having a hydroxyl group such as monoethanolamine, diethanolamine, 2-amino-2-methyl-1-propanol, tris(hydroxymethyl)aminomethane, etc. can also be used.

[0039] The above aqueous urethane resin is preferably contained in the total mass of the ink at 5 to 18% by mass, and more preferably at 5 to 15% by mass.

[0040] <Aqueous solvent> The printing ink of the present invention contains water as an aqueous solvent, but may also contain aqueous organic solvents such as alcohol-based, ketone-based, and ester-based solvents. From the perspective of environmental compatibility, alcohol-based organic solvents are preferred. Specifically, methanol, ethanol, n-propanol, isopropyl alcohol, 1-butanol, 2-methyl-1-propanol, 2-butanol, 2-methyl-2-propanol, ethylene glycol, propylene glycol, diethylene glycol, etc. can be mentioned. Among them, n-propanol and / or isopropyl alcohol are preferred. The organic solvent is preferably contained at 25% by mass or less, and more preferably 10% by mass or less in the total mass of the ink.

[0041] <Additive> The printing ink of the present invention can contain known additives such as surfactants, defoamers, thickeners, leveling agents, pigment dispersants, curing agents, and ultraviolet absorbers as necessary.

[0042] In order to stably disperse the pigment in the aqueous medium, it can be dispersed with the aqueous urethane resin alone, but a pigment dispersant can also be used in combination to more stably disperse the pigment. As the dispersant, surfactants such as anionic, nonionic, cationic, and amphoteric surfactants can be used. The dispersant is preferably contained in the ink at 0.05% by mass or more based on the total mass of the ink from the perspective of storage stability of the ink, and 5% by mass or less from the perspective of laminate strength. More preferably, it is in the range of 0.1 to 2% by mass.

[0043] In the present invention, the printing ink preferably contains an acetylene glycol-based compound and / or a styrene maleic acid-based compound from the perspective of pigment dispersibility.

[0044] The acetylene glycol-based compound is a nonionic compound with a symmetrical structure having an acetylene group in the center and is a surfactant. The acetylene glycol-based compound is more preferably an ethylene oxide adduct. By adding the acetylene glycol-based compound to the printing ink of the present invention, it contributes to the improvement of plate clogging resistance. The addition amount of the acetylene glycol-based compound is preferably 0.1 to 5% by mass, more preferably 0.3 to 3% by mass, based on 100% by mass of the ink. Commercially available products of the acetylene glycol-based compound include Orfin E1010, Orfin E1020 manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 104, Surfynol 420, Surfynol 440, Surfynol 465, Surfynol 485 manufactured by Air Products and Chemicals, Inc., and the like.

[0045] By adding the styrene maleic acid-based compound to the printing ink of the present invention, the leveling property and plate clogging resistance are improved. The styrene maleic acid-based compound may be an aqueous resin obtained by copolymerizing styrene and maleic acid, and examples thereof include styrene maleic acid monobutyl ester copolymer. The addition amount of the styrene maleic acid-based compound is preferably 0.1 to 3% by mass, more preferably 0.1 to 2% by mass, based on 100% by mass of the ink.

[0046] <Hardener> The printing ink of the present invention can improve the adhesion to the substrate, the laminate strength, and the water resistance by crosslinking the aqueous urethane resin using a hardener. Since the aqueous urethane resin has a carboxyl group, it is preferable to use a carbodiimide compound or an epoxy compound as the hardener. The carbodiimide compound is a compound having a carbodiimide group, and examples thereof include Carbodilite E-02, E-03A, SV-02, V-02, V02-L2, V-04 manufactured by Nisshinbo Industries, Inc. The epoxy compound refers to a compound having an epoxy group, and examples thereof include alicyclic epoxies such as Adeka Resin EP-4000, EP-4005, 7001 manufactured by ADEKA Corporation. The hardener is preferably used in an amount of 0.05 to 5% by mass, more preferably 0.1 to 3% by mass, based on the total mass of the ink.

[0047] <Other resins> In addition, an aqueous resin other than the above aqueous urethane resin may be included as a binder resin of the ink as long as the gist of the present invention is not impaired. Examples of such resins include conventional aqueous urethane resins other than the above aqueous urethane resin, aqueous polyester resins, aqueous acrylic resins, aqueous styrene-acrylic resins, aqueous rosin-modified maleic acid resins, aqueous cellulose-based resins, aqueous vinyl chloride copolymer resins, and aqueous chlorinated polyolefins. A plurality of these can also be used in combination.

[0048] <Manufacture of printing ink> The method for manufacturing the printing ink of the present invention is not particularly limited, but can be preferably manufactured by mixing or dispersing the compounding components using, for example, a ball mill, an attritor, or a bead mill. For example, it can be manufactured by mixing a pigment, an aqueous urethane resin, and water with a disper for about 20 minutes and then dispersing them with a sand mill or other bead mill for about 10 minutes.

[0049] The ink viscosity of the printing ink manufactured by the above method is preferably in the range of 10 mPa·s or more from the viewpoint of preventing sedimentation of the pigment and appropriately dispersing it, and 1000 mPa·s or less from the viewpoint of workability efficiency during ink production and printing. The above viscosity is the viscosity measured at 25°C with a B-type viscometer manufactured by Toki Sangyo Co., Ltd.

[0050] The printing ink of the present invention preferably has a biomass content of 10% by mass or more by using at least one of the coloring agent, aqueous urethane resin, and wax contained therein as a biomass-derived material.

[0051] <Printed matter> The printing ink of the present invention can be printed on the surface of a substrate to form a printed layer, resulting in a printed matter. Depending on the intended printed matter, it can be used, for example, in the plate system of the gravure printing method or the flexographic printing method.

[0052] The printed layer formed using the printing ink of the present invention can be used in a laminate for laminating two or more substrates. When there is a printed layer formed from the ink of the present invention between two substrates, it is called reverse printing. In the present invention, "for lamination" means a usage form as a laminate having a substrate 1, a printed layer formed using the printing ink of the present invention, and a substrate 2 in this order. It is also preferable to have an adhesive layer between the printed layer and the substrate 2.

[0053] (Substrate, Substrate 1) The type and thickness of the substrate are not particularly limited, but it is preferably a paper substrate or a plastic film. Examples of the type of substrate include polyester-based substrates, nylon (polyamide) substrates, polyolefin substrates, and vapor depositions of these metal oxides. In the case of a polyolefin substrate, a corona discharge-treated polyolefin substrate having a functional group such as a hydroxyl group or a carbonyl group can be used to obtain a good printed matter. The plastic substrate is preferably a uniaxially or biaxially stretched substrate. The printed matter is always treated as a wound product and is cut into a specific size through a lamination process, a slitting process, etc. as necessary.

[0054] (Substrate 2) The substrate 2 may be the same as or different from the substrate 1, and preferably has thermoplasticity (heat sealability). For example, an unstretched polyolefin substrate can be mentioned.

[0055] The method for manufacturing a printed matter using the printing ink of the present invention includes printing on the surface of a wound plastic substrate using the printing ink of the present invention. After printing, processes such as lamination, slitting (cutting unnecessary parts of the width), and bag making (cutting and heat sealing to form a bag) can be performed.

[0056] Both the gravure printing method and the flexographic printing method are of a winding type for printing, enabling high-speed printing and excellent productivity. In gravure printing, a gravure plate with cells (recesses) for expressing patterns and / or characters is usually used on the circumferential surface of a cylindrical cylinder. The cells are filled with printing ink, and the printed object (plastic substrate) is passed through under pressure between the gravure plate and the impression cylinder, thereby transferring the printing ink filled in the cells to the printed object to reproduce patterns and / or characters on the printed object. In flexographic printing, ink is supplied directly from a container for storing the printing ink or via an ink supply pump or the like to an anilox roller having an uneven shape on its surface. The ink supplied to this anilox roller is transferred to the printing plate surface by contact with the convex portions of the printing plate surface, and further transferred to the plastic substrate finally by contact between the printing plate surface and the plastic substrate, forming patterns and / or characters.

[0057] Since the plastic substrate is of a winding type, it is in the form of a roll aligned to a specified width. Therefore, it is different from the sheet-fed paper in which each sheet is pre-separated. The width of the substrate is appropriately selected based on the plate width of the printing machine to be used and the width of the image (pattern) portion of the gravure plate. When printing with multiple colors of printing ink overlaid, the order of these inks is not particularly limited.

[0058] When printing in the gravure printing and flexographic printing methods, in the case of reverse printing, it is common to print the color ink first and then the white ink on the wound plastic substrate. When there are multiple colors of color ink, for example, they can be printed in the order of black, cyan, magenta, and yellow, but there is no particular limitation. In addition, in a large printing machine, in addition to the basic colors, special colors and the like can be used. That is, a large printing machine has a plurality of printing units corresponding to 5 to 10 colors, and each printing unit is equipped with one color of ink, and 5 to 10 colors of overprinting can be performed at once.

Example

[0059] Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to these examples as long as it does not deviate from the technical idea of the present invention.

[0060] <Weight average molecular weight> The weight average molecular weight (Mw) was measured by GPC (gel permeation chromatography) and determined as the converted molecular weight using polystyrene as a standard substance. The measurement conditions are shown below. GPC apparatus: Shodex GPC-104 manufactured by Showa Denko KK Columns: The following columns were connected in series and used. Two Shodex LF-404 manufactured by Showa Denko KK Shodex LF-G manufactured by Showa Denko KK Detector: RI (differential refractometer) Measurement conditions: Column temperature 40°C Eluent: Tetrahydrofuran Flow rate: 0.3 mL / min

[0061] <Hydroxyl value and acid value> Determined according to the method described in JIS K0070.

[0062] [Synthesis Example 1] (Synthesis of aqueous urethane resin P1 solution) While introducing nitrogen gas into a reactor equipped with a reflux cooling tube, a dropping funnel, a gas introduction tube, a stirring device, and a thermometer, 41.8 parts of polyethylene glycol with a number average molecular weight of 2,000 (PEG2000), 11.8 parts of polyethylene glycol with a number average molecular weight of 1,000 (PEG1000), 167.2 parts of polytetramethylene glycol with a biomass degree of 92% and a molecular weight of 2,000 (bioPTMG2000), 34.8 parts of 2,2-dimethylolbutanoic acid (DMBA), 0.7 part of 2,2-dimethylolpropanoic acid (DMPA), and 200 parts of methyl ethyl ketone (MEK) were mixed. While stirring, 112 parts of isophorone diisocyanate (IPDI) was added dropwise over 1 hour, and the reaction was carried out at 80 °C for 4 hours to obtain a terminal isocyanate prepolymer solution. To the obtained terminal isocyanate prepolymer, a mixture of 7.1 parts of isophorone diamine (IPDA), 8.7 parts of 2-aminoethylethanolamine (AEA), and 120 parts of isopropyl alcohol (IPA) was gradually added at room temperature, and the reaction was carried out at 40 °C for 2 hours to obtain a solvent-type polyurethane resin solution. Next, 15.5 parts of 25% aqueous ammonia and 880.4 parts of ion-exchanged water were gradually added to the solvent-type polyurethane resin solution and neutralized to make it water-soluble. After further distilling off MEK and IPA under reduced pressure, water was added to adjust the solid content, and an aqueous urethane resin P1 solution with a solid content of 24% was obtained. The values such as the acid value, hydroxyl value, and weight average molecular weight of the aqueous urethane resin P1 are shown in Table 1.

[0063] [Synthesis Examples 2 to 4, 6, 7] (Synthesis of Aqueous Urethane Resin P2 to P4, P6, P7 Solutions) Except for using the raw materials and charging ratios described in Table 1, aqueous urethane resin P2 to P4, P6, P7 solutions were obtained by the same operations as in Synthesis Example 1. The values such as the acid value, hydroxyl value, and weight average molecular weight Mw of each resin are shown in Table 1.

[0064] [Synthesis Example 5] (Synthesis of Aqueous Urethane Resin P5 Solution) While introducing nitrogen gas into a reactor equipped with a reflux cooling tube, a dropping funnel, a gas introduction tube, a stirring device, and a thermometer, 95.9 parts of PEG2000, 116.9 parts of polytetramethylene glycol with a number average molecular weight of 2000 (PTMG2000), 35.2 parts of DMBA, 0.3 parts of DMPA, 24.8 parts of N-phenyldiisopropanolamine (PDIA), 4.8 parts of cyclohexanedimethanol (CHDM), 0.7 parts of trimethylolpropane, and 105.5 parts of IPDI were mixed and reacted at 90 °C for 8 hours while stirring to obtain a solvent-type polyurethane resin solution with terminal hydroxyl groups. Next, 160 parts of isopropyl alcohol (IPA) was gradually added and diluted at 70 °C, and 7.0 parts of 25% aqueous ammonia and 1048.9 parts of ion-exchanged water were gradually added and neutralized to make it water-soluble. After further distilling off IPA under reduced pressure, water was added to adjust the solid content, and an aqueous urethane resin P5 solution with a solid content of 24% was obtained. Values such as the acid value, hydroxyl value, and weight average molecular weight of the aqueous urethane resin P5 are shown in Table 1.

[0065] Among the aqueous urethane resins P1 to P7, the aqueous urethane resins P1 to P3 are made from polyols derived from biomass.

Table 1

[0066] Note that the abbreviations described in Table 1 represent the following. · PEG1000: Polyethylene glycol with a number average molecular weight of 1,000 · PEG2000: Polyethylene glycol with a number average molecular weight of 2,000 · PTMG2000: Polytetramethylene glycol with a number average molecular weight of 2,000 · Biomass PTMG2000: Polytetramethylene glycol with a biomass content of 92% and a number average molecular weight of 2,000 · PMPA: Adipic acid·3-methylpentane-1,5-diol polymer · C-2090: Dimethyl carbonate·1,6-hexanediol·3-methyl-1,5-pentanediol polycondensate · DMPA: 2,2-Dimethylolpropanoic acid ·DMBA: 2,2 - Dimethylolbutanoic acid ·PDIA: N,N - Bis(2 - hydroxypropyl)aniline ·CHDM: 1,4 - Cyclohexanedimethanol ·IPDA: Isophoronediamine ·AEA: 2 - Aminoethylethanolamine ·IBPA: Iminobispropylamine ·MEA: Monoethanolamine ·IPA: Isopropyl alcohol

[0067] [Example 1] (Production of white printing ink S1) 40.0 parts of titanium oxide (Titon R - 7E; manufactured by Sakai Chemical Industry Co., Ltd.), 10.6 parts of aqueous urethane resin P5 solution (solid content 24%), 0.1 part of defoaming agent BYK - 012 (manufactured by BYK - Chemie Japan), 3.6 parts of biomass resin particles A - 1 as wax (resin particles containing 98% of biomass - derived polyhydroxyalkanoic acid having a structural unit of general formula (1), average particle diameter 5 μm, Mw 400,000), 0.6 part of 10% aqueous ammonia, 2.0 parts of n - propyl alcohol (NPA), and 8.3 parts of water were stirred and mixed, dispersed with a sand mill, and then 21.0 parts of aqueous urethane resin P1 solution (solid content 24%), 0.1 part of adipic acid dihydrazide (ADH), and 13.7 parts of water were stirred and mixed to obtain white printing ink S1.

[0068] [Examples 2 - 14, Comparative Examples 1 - 5] (Production of white printing inks S2 - S14, SS1 - SS5) White printing inks S2 - S14, SS1 - SS5 were obtained in the same manner as in Example 1, except that the raw materials and charging ratios shown in Table 2 were used.

[0069] [Example 15] (Production of blue printing ink S15) 16.0 parts of copper phthalocyanine blue (Phthalocyanine Pigment Lionol Blue FG-7348, manufactured by Toyo Color Co., Ltd.), 38.0 parts of aqueous urethane resin P6 solution (solid content 24%), 0.1 part of defoaming agent BYK-012 (manufactured by BYK Japan Co., Ltd.), 1.3 parts of biomass resin particles A-1 as wax (resin particles containing 98% of biomass-derived polyhydroxyalkanoic acid having a structural unit of general formula (1), average particle diameter 5 μm, Mw 400,000), 7.0 parts of n-propyl alcohol (NPA), 0.7 part of 10% aqueous ammonia, and 2.8 parts of water were stirred and mixed, dispersed with a sand mill, then 23.0 parts of aqueous urethane resin P1 solution (solid content 24%), 0.9 part of Surfynol 465 (acetylene glycol-based compound, manufactured by Air Products Japan Co., Ltd., solid content 100%), 0.1 part of adipic acid dihydrazide (ADH), and 9.1 parts of water were stirred and mixed to obtain blue printing ink S15.

[0070] [Examples 16 to 27, Comparative Examples 6 to 10] (Manufacture of Blue Printing Inks S16 to S27, SS6 to SS10) Blue printing inks S16 to S27 and SS6 to SS10 were obtained in the same manner as in Example 15, except that the raw materials and charging ratios shown in Table 3 were used. Note that the waxes described in Tables 2 and 3 are as follows. · Biomass resin particles A: Resin particles containing 98% of biomass-derived polyhydroxyalkanoic acid having a structural unit of general formula (1) with respect to the whole wax R 1 having 3 carbon atoms Biomass resin particles A-1: Average particle diameter 5 μm, Mw 400,000 Biomass resin particles A-2: Average particle diameter 5 μm, Mw 2,000,000 Biomass resin particles A-3: Average particle diameter 5 μm, Mw 20,000 Biomass resin particles A-4: Average particle diameter 2 μm, Mw 400,000 Biomass resin particles A-5: Average particle diameter 10 μm, Mw 400,000 · Biomass resin particles B: Wax containing 100% of biomass-derived polylactic acid having a structural unit of general formula (1) with respect to the whole wax, average particle diameter 2 μm, Mw 20,000 · Carnauba wax: A wax containing 100% of carnauba wax derived from biomass containing 35% of the structural unit of the general formula (1) with respect to the whole wax, average particle diameter 5 μm, Mw 1000 · Polyethylene wax: Synthetic polyethylene-based wax, 5 μm, Mw 4000 Also, the acrylic resins described in Table 2 and Table 3 are as follows. · Joncryl 63J: Solids content 30%, water-soluble acrylic, manufactured by BASF Japan Ltd.) · Joncryl 632: Solids content 42%, acrylic emulsion, manufactured by BASF Japan Ltd.) The styrene maleic acid-based resin in Table 3 is as follows. · Styrene maleic acid-based resin: Solids content 22.5%, molecular weight 17,000, acid value 185 mg / KOH

[0071] (Preparation of the printed matter of Example 1) (Preparation of Printed Matter 1 using Ink S1) [Polypropylene (OPP) substrate / Printing layer] Gravure printing: The Ink S1 obtained above was adjusted to 16 seconds with a Zahn cup #3 (manufactured by Rika K.K.) using a mixed solvent of water / n-propanol (mass ratio 1 / 1), and printed on an OPP substrate (FOR-AQ film thickness 20 μm (manufactured by Futamura Chemical Co., Ltd.)) at a speed of 50 m / min using a gravure printing machine manufactured by Iwase Printing Machinery Co., Ltd., and dried at 50 °C to obtain a printed matter. For the plate, an etched 250-line plate with a depth of 15 μm solid plate was used. Using this printed matter, evaluation of plate clogging resistance, humidity-resistant blocking resistance, scratch resistance, and tape adhesiveness was carried out.

[0072] (Printed matters of Examples 2 to 27 and Comparative Examples 1 to 10) For the above Inks S2 to S27 (Examples) and SS1 to SS10 (Comparative Examples), printed matters were obtained in the same manner as S1.

[0073] [Characteristic evaluation] Using inks S1 to S27 (Examples), SS1 to SS10 (Comparative Examples), and the printed matter using them, evaluations of two-component stability over time, plate clogging resistance, humidity resistance blocking property, scratch resistance, and tape adhesiveness were carried out by the methods described below.

[0074] <Two-component stability over time> Regarding inks S1 to S27 (Examples) and SS1 to SS10 (Comparative Examples), each ink and a dilution solution (a mixed solution of ethanol:isopropanol:water = 20:20:60) were mixed at a ratio of ink:dilution solution = 1:1. Then, a 5% carbodiimide aqueous dispersion solution (manufactured by Nisshinbo Co., Ltd.: Carbodilite E-02) was added to the ink as a curing agent and stirred to prepare test samples. The viscosity of this test sample was measured to obtain the initial viscosity. Then, it was left standing at a constant temperature of 40°C for one week, and the viscosity after aging was measured again to obtain the viscosity after aging. Next, the viscosity change before and after aging was calculated by the following formula. Viscosity change before and after aging (%) = ((viscosity after aging - initial viscosity) / initial viscosity) × 100 The evaluation criteria for the above viscosity change (%) are shown below. The practical level is 3 or more. 5 (practical level): Viscosity change before and after aging is less than 10% 4 (practical level): Viscosity change before and after aging is 10% or more and less than 20% 3 (practical level): Viscosity change before and after aging is 20% or more and less than 30% 2 (not practical): Viscosity change before and after aging is 30% or more 1 (not practical): Almost no fluidity

[0075] <Plate clogging resistance> The inks prepared in the examples and comparative examples were run idle for 60 minutes at a cylinder rotation speed of 150 m / min using a gravure rotary printing press equipped with a gravure plate with a plate depth of 15 μm and a doctor blade "K ceramic doctor 0.15×50 1460" (manufactured by Fuji Shogyo Co., Ltd.) with a blade tip thickness of 60 μm. Then, printing was performed at a printing speed of 150 m / min on the corona-treated surface of a corona-treated polyester film "Ester film E5100" (manufactured by Toyobo Co., Ltd.) with a thickness of 12 μm, and drying was carried out with hot air at 60°C to obtain a printed matter having non-image areas and image areas. The evaluation criteria are shown below. The practical level is 3 or higher. 5 (practical level): Even when 10 printed matters are stacked, no coloring derived from the ink is observed in the non-image areas. 4 (practical level): When 10 printed matters are stacked, coloring derived from the ink is observed in the non-image areas. 3 (practical level): When 5 printed matters are stacked, coloring derived from the ink is observed in the non-image areas. 2 (not practical): Even for a single printed matter, coloring derived from the ink is observed in the non-image areas. 1 (not practical): Even for a single printed matter, there is a lot of coloring derived from the ink in the non-image areas.

[0076] <Humidity-resistant blocking property> Using the printed inks prepared in the examples and comparative examples, the surface of the printed layer of the printed matter obtained by producing the printed matter and the non-corona-treated surface of an OPP base material (FOR-AQ film thickness 20 μm (manufactured by Futamura Chemical Co., Ltd.)) were pressure-bonded at 40°C and 5 kg / cm 2 , 80 RH% for 12 hours, and then the degree of peeling of the printed layer when the printed matter and the OPP base material were peeled off was evaluated. The practical level is 3 or higher. [Evaluation criteria] 5 (practical level): There is no peeling of the printed layer, and no resistance is felt. 4 (practical level): There is no peeling of the printed layer, but resistance is felt. 3 (practical level): There is slight peeling of less than 20% of the printed layer area. 2 (not practical): There is peeling of 20% or more and less than 50% of the printed layer area. 1 (not practical): There is peeling of 50% or more of the printed layer area.

[0077] <Scratch resistance> The printed matter produced in the above Examples and Comparative Examples is cut into a size of 10 cm × 5 cm immediately after printing as a test piece, and the degree of damage to the coating film when gently scratched 10 times on the back of a human nail is visually observed. The judgment criteria are shown below. The practical level is 3 or more. 5 (practical level): The test piece has no scratches at all. 4 (practical level): Slight scratches are visible on the test piece, but there are no continuous scratches. 3 (practical level): One continuous scratch is visible on the test piece. 2 (not practical): Two or more and five or less scratches are visible on the test piece. 1 (not practical): Six or more scratches are visible on the test piece.

[0078] <Tape adhesion> The printed matter produced in the above Examples and Comparative Examples is cut into a size of 10 cm × 10 cm immediately after printing as a test piece, a 7-mm-wide Nichiban cellophane tape is pasted 6 cm, and then the finger is rubbed 10 times from above. Then, 3 cm of the cellophane tape is slowly peeled off, and the remaining 3 cm is quickly peeled off. This operation is performed 3 times with the position changed, and the degree of peeling of the printed surface is observed and evaluated. The judgment criteria are shown below. The practical level is 3 or more. 5 (practical level): There is no peeling on the printed surface at all. 4 (practical level): There is no peeling on the printed surface of the part slowly peeled off, and there is less than 3% area peeling on the printed surface quickly peeled off. 3 (practical level): There is no peeling on the printed surface when slowly peeled off, and there is 3% area or more and less than 30% area peeling on the printed surface when quickly peeled off. 2 (not practical): There is no peeling on the printed surface when slowly peeled off, and there is 30% area or more peeling on the printed surface when quickly peeled off. 1 (not practical): There is peeling on the printed surface when slowly peeled off.

[0079] The evaluation results were summarized in Tables 2 and 3. Compared with the aqueous printing inks of Comparative Examples 1 to 10, the aqueous printing inks of Examples 1 to 27 had suppressed plate clogging during printing, and had good humidity-resistant blocking properties, scratch resistance, tape adhesiveness, and two-component stability over time after adding a curing agent to the printing ink. That is, according to the present invention, it was possible to provide an aqueous printing ink that solved the above problems.

[0080] [Table 2]

[0081] [Table 3]

Claims

1. A printing ink containing a colorant, an aqueous urethane resin, a wax, and an aqueous solvent, wherein the wax contains, based on the total amount of the wax, 50% by mass or more of a structural unit represented by the following general formula (1), the weight average molecular weight of the wax is from 1,000 to 2,400,000, and the printing ink contains 0.1 to 6% by mass of the wax based on the total amount of the printing ink. General formula (1) 【Chemical 1】 (R １ represents a hydrocarbon group having 1 to 24 carbon atoms.)

2. The printing ink according to Claim 1, wherein the structural unit represented by the general formula (1) is derived from biomass.

3. The printing ink according to Claim 1, wherein the aqueous urethane resin is made from a biomass-derived polyol as a raw material.

4. The printing ink according to Claim 1, wherein the particle size of the wax is from 0.1 to 10 μm.

5. The printing ink according to Claim 1, wherein the biomass degree of the printing ink is 10% by mass or more.

6. The printing ink according to Claim 1, which is a printing ink for back printing.

Images